A Feasibility Study Of Fixed-removable Partial Denture For Dentition Defect Simultaneously Fabricated With Subtractive/additive Manufacturing

The present situation of dentition defect in the domestic population is severe,and the removable partial denture(RPD)occupies a large proportion in clinical practice due to its wide indications and economic benefits.The traditional method for producing RPD is tedious.Especially in the situation of tooth defects of abutment tooth that need full crown restorations,the patients should be multiple visits and the doctor's clinical operation time increases.With the development of CAD/CAM technology in the field of prosthodontics,a variety of digital restoration programs have reduced the manpower and shortened the chair-side operation time while improving the accuracy of the prosthesis.Among them,3D printing technology is a new method for the processing of dental prostheses.It tends to be mature in the processing of metal restorations,such as metal crowns,metal frameworks,etc.However,there are some problems like sticky powders and cracks in the processing of all-ceramic restorations and affect its further application.Objective:A digital method that used 3D printing and Numerical-control milling was put forward to simultaneously manufacture fixed prosthesis of abutment of RPD and its supported RPD,to get rid of the tedious procedures of traditional method of RPD,and to improve the quality of restoration prosthesis.The dental restorations would be finished in two visits.At the same time,the feasibility of zirconia all-ceramic restorations fabricated with 3D printing is studied,which lays a foundation for the clinical application of zirconia restorations fabricated with 3D printing.Method and Contents: Design a digital solution that simultaneously manufacture fixed-removable denture restoration for patients with dentition defects.The feasibility of digital solution was analyzed by three-dimensional optical measurement method,three-dimensional measurement of silicon film method,and clinical studies.Mainly include the following: 1)The trueness and fit evaluation of single and union zirconia crowns fabricated with 3D printing.2)The fit evaluation of pure titanium frameworks that simultaneously manufactured with fixed restoration fabricated by 3D printing/Numerical-control milling.3)Fabricating simultaneously of fixed-removable partial denture for dentition defect using subtractive/additive manufacturing: a case report.Results: 1)Successfully presented a digital program that can simultaneously fabricate fixed-removable partial denture for patients with dentition defects,and the restorations were successfully fitted to the cast.2)The trueness in the different parts of single and union zirconia crowns fabricated with 3D printing is no significant difference from corresponding parts of single and union zirconia crowns fabricated with Numerical-control milling.The trueness of the inner part of the crown is better than that of the outer part.The color-maps shows that the trueness error mainly occurs in the large surfaces with curvature like grooves in occlusal surfaces and the line angle in the inner part,and the trueness of the remaining parts and the marginal part is normal.3)The marginal fit of the single and union zirconia crowns fabricated with 3D printing reached the clinically accepted range of 120 ?m,and the fit of marginal and internal of them was no significant difference from them fabricated with Numerical-control milling.4)The fit of the frameworks is 0-300?m manufactured by 3D printing.And the fit of occlusal rests and combined clasps was better than the fit of the large connector and the metal base.5)The marginal fit of the union all-ceramic crowm manufactured by 3D printing seated on the abutment of RPD framework was within 150 ?m,but the internal fit was increased due to the metal loss caused by the polishing and finishing.6)Randomly selected one patient with dentition defect to perform the digital solution in this study and found that the 3D printed all-ceramic crown was successfully fitted to the patient.The RPD was fitted properly on the patient and good retention,as well as clinically seamless contacts between the marginal of metal base and oral mucous.The tilting of the PRD was not found.The fit checker indicated uniform contact between the RPD and the mucous and there was no obvious tender points.Discomfort was not found during the follow-up and the patient was satisfied with the finished RPD.Conclusion: It is feasible to use the 3D printing/Numerical-control milling technology to simultaneously manufacture the fixed prosthesis of abutment tooth and the supporting RPD.This method achieves a good quality of the restorations,reduces the number of patient visits and the chairside operating time.In addition,the trueness and fit of zirconia all-ceramic crowns produced by 3D printing can meet the requirements of clinical use.It is a candidate technique for producing oral zirconia all-ceramic restorations.